NEAR-INFRARED SPECTRA OF IC 59/63 AND NGC 1535: COMPARING INFRARED AND ULTRAVIOLET OBSERVATIONS OF H_2

摘要

We present observations of near-infrared H_2 line emission toward the reflection/emission nebulae, IC 59 and IC 63, and the planetary nebula, NGC 1535. Each source has been observed previously in the ultraviolet, where H_2 was detected in emission toward IC 63 and in absorption toward NGC 1535. In IC 63, we have detected the 1.601 μm v = 6-4 Q(1), 2.121 μm v = 1-0 S(1), and 2.247 μm v = 2-1 S(1) lines of H_2 arising from a near-infrared fluorescent cascade following ultraviolet continuum pumping. The detection marks the first time that both infrared and ultraviolet portions of the H_2 fluorescent cascade have been measured in a region exposed to far-ultraviolet continuum photons. Furthermore, we also report 1-0 S(1) and 2-1 S(1) fluorescent emission toward IC 59, a source previously thought to display no H_2 fluorescence and considered devoid of molecules based on ultraviolet and CO observations. Toward NGC 1535, we find no H_2 emission in the near-infrared, in spite of the reported ultraviolet H_2 absorption.